The harmful combustion products produced by a conventional diesel engine include nitrogen oxides (NOx), carbon monoxide (CO), and various hydrocarbons formed from the incomplete combustion of the diesel fuel. Other gaseous emissions include oxides of sulfur, generally referred to as SOx. Also, solid carbon particles are produced which enter the exhaust in the form of soot or ash, also known as particulate matter (or PM).
Oxides of nitrogen (NO and NO2) are a considerable component of diesel engines emissions. These oxides of nitrogen (referred to collectively as NOx) are known to be poisonous to the environment and dangerous to human health. Once dispersed into the atmosphere, NOx decomposes and contributes to air pollution and acid rain.
It is desirable to reduce the harmful emissions from diesel engines, particularly NOx emissions. Previous attempts to reduce NOx emissions have typically resulted in tradeoffs such as an increase in the other harmful emissions produced by the diesel engines or increased fuel consumption. It is therefore an object of the present invention to reduce harmful emissions, particularly of NOx, without such emission tradeoffs and increased fuel consumption.